International Journal of Engineering & Science Research

International Journal of Engineering & Science Research CFD ANALYSIS AND EXPERIMENTAL VERIFICATION OF EFFECT OF MANIFOLD GEOMETRY ON VOLUMETRIC EFFICIENCY AND BACK PRESSURE FOR MULTI- CYLINDER SI ENGINE ABSTRACT KS Umesh* 1, VK Pravin 2, K Rajagopal 3 1 Dept. of Mech. Engg, Thadomal Shahani Engineering College, Mumbai, Maharastra, India 2 Dept. of Mech. Engg, P.D.A. College of Engg., Gulbarga, Karnataka, India. 3 Former Vice Chancellor, JNT University, Hyderabad (AP), India. In internal combustion engines, volumetric efficiency is one of the prime factors in determining how much power output an engine can generate as compared to its capacity. The purpose of this research work is to investigate using CFD whether design of exhaust manifold has any impact on volumetric efficiency of the multi-cylinder SI engine and if any verify those results obtained through CFD analysis via actual experiments. The scope of the research is further stretched to investigate whether exhaust geometry has any impact on mechanical efficiency of the multi-cylinder SI engine. Flow of the exhaust gases through exhaust manifold is simulated using ANSYS FLUENT V12.0 using pressure and velocity parameters as boundary condition. The analysis has been carried out on two designs an existing one and a modified one and results are subsequently compared. It was observed that the volumetric efficiency improved drastically upon modification in exhaust geometry. Physical models of the same these two systems were subsequently manufactured and exhaustive experiments were carried out on them. The results obtained through CFD analysis were experimentally confirmed. Keywords: Manifold, Volumetric Efficiency, Multi-cylinder Engine, ANSYS FLUENT, Existing model. 1. INTRODUCTION In any multi-cylinder IC engine, an exhaust manifold (also known as a header) collects the exhaust gases from multiple cylinders into one pipe. It is attached downstream of the engine and is major part in multi cylinder engines where there are multiple exhaust streams that have to be collected into a single pipe. When an engine starts its exhaust stroke, the piston moves up the cylinder bore, increasing the pressure. When the exhaust valve opens, the high pressure exhaust gas enters into the exhaust manifold or header, creating an exhaust pulse comprising three main parts: The high pressure head is created by the large pressure difference between the exhaust in the combustion chamber and the atmospheric pressure outside of the exhaust system. As the exhaust gases equalize between the combustion chamber and the atmosphere, the difference in pressure decreases and the exhaust velocity decreases. This forms the medium pressure body component of the exhaust pulse. The remaining exhaust gas forms the low pressure tail component. This tail component may initially match ambient atmospheric pressure, but the momentum of the high and medium pressure components reduces the pressure in the combustion chamber to a lower than atmospheric level. This relatively low pressure (known as back pressure) helps to extract all the combustion products from the cylinder. Thus back pressure is one of the most critical parameter for exhaust system. Also lower back pressure helps to induct the intake charge during the overlap period when both intake and exhaust valves are partially open. The effect is known as scavenging. Scavenging efficiency is function of Length of the exhaust manifold, cross sectional area, shaping of the exhaust ports and pipe works influences the degree of scavenging effect and the engine speed range over which scavenging occurs. The magnitude of the exhaust scavenging effect is a direct function of the velocity of the high and medium pressure components of the exhaust pulse. Headers are designed to increase the exhaust velocity as much as possible. One technique is tuned length primary tubes. This technique attempts to time the occurrence of each exhaust pulse, to occur one after the other in succession while still in the exhaust system. The lower *Corresponding Author www.ijesr.org 342

pressure tail of an exhaust pulse then serves to create a greater pressure difference between the high pressure head of the next exhaust pulse, thus increasing the velocity of that exhaust pulse. ive work has taken place already in this field. Scheeringa et al studied analysis of Liquid cooled exhaust manifold using CFD. Detailed information of flow property distributions and heat transfer were obtained by him to improve the fundamental understandings of manifold operation. A number of computations were performed by him to investigate the parametric effects of operating conditions and geometry on the performance of manifolds. Seenikannan et al analysed a Y section exhaust manifold system experimentally to improve engine performance. His paper investigates the effect of using various models of exhaust manifold on CI engine performance and exhaust emission. Yasar Deger et al did CFD-FE-Analysis for the Manifold of a Diesel Engine aiming to determine specific temperature and pressure distributions. The fluid flow and the heat transfer through the exhaust manifold were computed correspondingly by CFD analyses including the conjugate heat transfer. 2. DISCUSSION Model Description Two different Models considered for this research work are shown in the figure 1 & 2 respectively. Fig 1: Existing Model Fig 2: Modified Model Both existing model and modified model has header length of 335mm. ID and OD of headers is 52.48 mm & 60.3 mm respectively. In existing model the bend radius is 48 mm and exhaust is on one side as shown in the figure. Modified model has bend radius of 100 mm and exhaust is at the centre of header. ID & OD of the bend & exhaust is 35.08mm and 42.2mm respectively for both models. 3. METHODOLOGY Both the models considered for this work were prepared using SOLIDWORKS. These models were imported into ANSYS CFX V12.0. The fluid body was subsequently generated from existing models using design Modular in ANSYS and subsequently meshed as shown in figures. Fig 3: Fluid Body (Existing Model) Fig 4: Existing Manifold (After Meshing) Copyright 2013 Published by IJESR. All rights reserved 343

Fig 5: Fluid Body (Modified Model) Fig 6: Modified Manifold (After Meshing) A steady state single species simulation will be carried out under isothermal conditions for exhaust gas. Turbulence will be modeled by k-ε RNG turbulence model appropriate to account for high velocities and strong streamline curvature in the flow domain. The reference pressure will be set at 1 atm and all pressure inputs and outputs will be obtained as gauge values with respect to this. 4. MATERIAL FLUID PROPERTIES gas will be considered as an incompressible fluid operating at 230 280 0 C. The material properties under these conditions are Table 1: Material Fluid Properties Boundary Conditions Material Air + Gasoline Density (kg/m3) 1.0685 Viscosity (Pa-s) 3.0927 x 10 5 Specific heat (J/kg-K) 1056.6434 Thermal conductivity (W/m-K) 0.0250 The engine speed was maintained at 1500 RPM and results were obtained at different load Conditions viz. 2kg, 4kg, 6k, 8kg and 12 kg. The atmospheric gauge pressure was set at 0. And pressure distribution was obtained. 5. EXPERIMENTAL SET-UP Two models considered for the work were manufactured. The material used for pipe was SA106 (Grade B). Flange Material was IS 2062 (Grade B). Elbows were manufactured using SA 234 WPB. Fig 7: Existing model (left) and Modified Model (Right) Copyright 2013 Published by IJESR. All rights reserved 344

The test was conducted on 4 stroke 4 cylinder Engine of Maruti-Suzuki make. Experimental set up consisted of: (1) The engine & dynamometer fitted together on common channel frame (2) Fuel Consumption measuring unit & temperature measuring units (3) gas Calorimeter (4) Orifice Meter The experimental set up is shown in the figure. Fig 8: Experimental set up (a) s were measured at (b) Gas inlet to the calorimeter (c) gas outlet to calorimeter (d) Water inlet to calorimeter (e) Water outlet from Calorimeter (f) Water outlet from Engine Also pressure and temperatures were measured in header at points where bends are attached and in the exhaust. Engine Specifications Copyright 2013 Published by IJESR. All rights reserved 345

Table 2: Engine Specification 6. RESULTS Engine 4 Stroke 4 Cylinder SI engine Make Maruti-Suzuki Wagon-R Calorific Value of Fuel (Gasoline) 45208 KJ/Kg-K Specific Gravity of Fuel 0.7 gm/cc Bore and Stroke 69.05 mm X 73.40 mm Swept Volume 1100 cc Compression Ratio 7.2 :1 Dynamometer Constant 2000 Diameter of Orifice 29 mm Coefficient of Discharge of orifice 0.65 CFD analysis was carried out on both the models at 6 different loads. 2kg, 4kg, 6kg, 8kg, 10kg and 12 kg. The resulting pressure contour for 4 kg loading is shown in the figure for both the models. The experiments were conducted with same loading conditions on same two models and results obtained after the calculation are enlisted in following table Fig 9: contours for existing and Modified Models The experiments were conducted with same loading conditions on same two models and results obtained after the calculations are enlisted in following tables. Qs and Qa specify swept volume and air intake respectively. Thus their ratio gives volumetric efficiency. Also morse test was conducted on engines to evaluate their Indicated power (I.P.). Brake power (B.P.) was experimentally determined using dynamometer. Thus Mechanical efficiency was also evaluated as ratio of B.P. to I.P. The pressures P1, P2, P3, P4, P5 and temperatures T1, T2, T3, T4, T5 were measured at exhaust manifold and points where 4 inlet bends are attached to header. was calculated using ideal gas equation. These are instantaneous velocities of exhaust gas at above mentioned points. Table 3: Results of experiments conducted on existing Model Unit 2 KG 4 KG 6 KG 8 KG 10 KG 12 KG Column1 B.P. (kw) KW 1.119 2.238 3.357 4.476 5.595 6.71 Heat Equivalent Kj/min 67.14 134.2 201.4 268.5 335.7 402 Fuel Consumption cc/min 87.77 90.36 94.88 106.2 107.1 112 gm/min 61.43 63.25 66.41 74.34 74.97 78.8 Heat Supplied Kj/min 2777.5 2859.5 3002.5 3360.8 3389.2 3566 Heat Carried By water Kj/min 477.3 891 938.7 970.5 986.5 970. Copyright 2013 Published by IJESR. All rights reserved 346

MgCpg Kj/Kg C 1.446 1.185 1.377 1.545 1.64 1.72 Heat Carried by Kj/min 407.8 426.6 526 599.5 623.2 629 Unaccounted Heat Loss Kj/min 1825 1407 1336 1522 1443 1564 Qs *10-3 m 3 13.75 13.75 13.75 13.75 13.75 13.7 Qa *10-3 m 3 8.068 7.606 8.714 9.696 10.24 10.9 Volumetric Efficiency 58.67 55.32 63.37 70.52 74.47 79.4 Air : Fuel Ratio 9.454 8.658 9.447 9.391 9.834 9.97 B.S.F.C. Kg-Hr/ KW 3.294 1.695 1.187 0.996 0.804 0.70 p1 mm of water 90 131 169 196 198 223 p2 mm of water 121 168 213 251 261 289 p3 mm of water 102 142 186 222 225 255 p4 mm of water 122 163 210 252 265 296 p5 mm of water 126 167 216 255 265 296 t1 Celsius 303 381 403 409 401 385 t2 Celsius 335 423 449 456 451 441 t3 Celsius 540 630 630 661 665 690 t4 Celsius 344 424 425 432 418 403 t5 Celsius 284 371 389 390 381 370 v1 m/s 15.87 16.92 19.97 22.36 23.33 24.2 v2 m/s 4.176 4.487 5.310 5.945 6.229 6.53 v3 m/s 5.594 5.836 6.658 7.638 8.098 8.84 v4 m/s 4.237 4.496 5.135 5.749 5.943 6.18 v5 m/s 3.824 4.152 4.868 5.405 5.625 5.88 ma + mf (Kg/s) *10-3 kg/s 10.70 10.18 11.56 12.87 13.53 14.4 Morse test(all Cylinder) Kg 2 4 6 8 10 12 Morse test (1 st cylinder) Kg 1.4 2.95 4.6 6.2 7.4 8.8 Morse test(2 nd cylinder) Kg 1.4 2.90 4.6 6.15 7.35 8.8 Morse test (3 rd cylinder) Kg 1.35 2.85 4.55 6.1 7.35 8.85 Morse test (4 th cylinder) Kg 1.35 2.85 4.6 6.1 7.35 8.85 I.P. (1st) Kw 0.400 0.65 0.783 1.225 1.55 1.80 I.P. (2nd) Kw 0.400 0.605 0.783 1.15 1.485 1.80 I.P. (3rd) 0.375 0.575 0.811 1.15 1.485 1.85 I.P. (4th) Kw 0.375 0.575 0.783 1.225 1.485 1.85 IP Kw 1.45 2.5 3.65 4.985 6.225 7.55 Mechanical Efficiency Percentage 80 88.75 94.16 93.12 93 90.8 Frictional Power Kw 0.223 0.251 0.195 0.307 0.391 0.61 Table 4: Results of experiments conducted on modified Model Column1 Unit 2 KG 4 KG 6 KG 8 KG 10 KG 12 KG B.P. (kw) KW 1.119 2.238 3.357 4.476 5.595 6.714 Heat Equivalent Kj/min 67.14 134.28 201.42 268.56 335.7 402.87 Fuel Consumption cc/min 114.5 122.14 123.96 131.59 133.9 136.36 Copyright 2013 Published by IJESR. All rights reserved 347

gm/min 80.15 85.504 86.776 92.117 93.75 95.454 Heat Supplied Kj/min 3623.4 3865.4 3922.9 4164.4 4238 4315.2 Heat Carried By Water Kj/min 175.08 254.56 381.85 556.87 715.9 715.97 MgCpg Kj/Kg C 1.48 1.53 1.4248 1.6748 1.94 1.725 Heat Carried by Kj/min 324.12 361.08 386.12 534.26 715.8 662.4 Unaccounted Heat Loss Kj/min 3057.0 3115.5 2953.5 2804.7 2470 2534.0 Qs *10-3 m 3 13.75 13.75 13.75 13.75 13.75 13.75 Qa *10-3 m 3 9.5 10.757 10.58 12.17 12.17 11.41 Volumetric Efficiency 69.090 78.232 76.945 88.509 88.50 82.981 Air : Fuel Ratio 8.534 9.0580 8.7784 9.5121 9.346 8.6064 B.S.F.C. Kg-Hr/ KW 4.2975 2.2923 1.5509 1.2348 1.005 0.8530 p1 mm of water 89 107 147 173 225 235 p2 mm of water 122 145 200 240 295 308 p3 mm of water 117 138 183 220 275 292 p4 mm of water 120 140 183 227 280 290 p5 mm of water 124 146 188 253 298 309 t1 Celsius 240 257 292 340 390 405 t2 Celsius 234 162 220 259 342 380 t3 Celsius 233 237 297 313 369 394 t4 Celsius 229 230 270 341 383 395 t5 Celsius 131 135 184 318 368 374 v1 m/s 16.646 19.440 20.306 25.281 27.21 26.065 v2 m/s 4.1001 3.9747 4.4079 5.4511 6.269 6.2339 v3 m/s 4.0939 4.6630 5.1044 6.0156 6.557 6.3770 v4 m/s 4.0604 4.5982 4.8626 6.2989 6.696 6.3877 v5 m/s 3.2665 3.7267 4.0906 6.0484 6.533 6.1761 ma + mf (Kg/s) *10-3 kg/s 12.735 14.333 14.142 16.139 16.16 15.282 Morse test(all Cylinder) Kg 2 4 6 8 10 12 Morse test (1 st cylinder) Kg 1.4 2.95 4.6 6.2 7.4 8.8 Morse test(2 nd cylinder) Kg 1.4 2.90 4.6 6.15 7.35 8.8 Morse test (3 rd cylinder) Kg 1.4 2.85 4.55 6.1 7.35 8.85 Morse test (4 th cylinder) Kg 1.35 2.85 4.6 6.1 7.35 8.85 I.P. (1st) Kw 0.400 0.65 0.783 1.225 1.55 1.80 I.P. (2nd) Kw 0.400 0.605 0.783 1.15 1.485 1.80 I.P. (3rd) 0.400 0.575 0.811 1.15 1.485 1.85 I.P. (4th) Kw 0.375 0.575 0.783 1.225 1.485 1.85 IP Kw 1.375 2.5 3.65 4.985 6.225 7.55 Mechanical Efficiency Percentage 77.5 90 90 91.25 93 90 Frictional Power Kw 0.25178 0.2238 0.3357 0.39165 0.3916 0.6714 Aim of the work was to verify all the results obtained through CFD analysis by experimentation. Thus the results obtained through CFD analysis and experiments have been compared in following two tables for both the models at all load conditions. Copyright 2013 Published by IJESR. All rights reserved 348

Table 5: Comparison between theoretical results (Using CFD) and Experimental results For existing Model 2 Kg from ( Experimental) -0.0425 1275.3 121 1187.01 4.225 4.176 335 0.0425 1079.1 102 1000.62 5.412 5.594 540 0.1275 1275.3 122 1196.82 4.225 4.237 344 0.2125 1324.35 126 1236.06 3.485 3.824 284 4 Kg from ( Experimental) -0.0425 1579.41 168 1648.08 4.375 4.487 423 0.0425 1471.5 142 1393.02 5.45 5.836 630 0.1275 1579.41 163 1599.03 4.375 4.495 424 0.2125 1716.75 167 1638.27 4.02 4.152 371 6 Kg from ( Experimental) -0.0425 1962 213 2089.53 5.125 5.31 449 0.0425 1765.8 186 1824.66 5.994 6.658 630 0.1275 1962 210 2060.1 5.125 5.135 425 0.2125 2207.25 216 2118.96 4.758 4.868 389 8 Kg from ( Experimental) -0.0425 2345.4 251 2462.31 5.485 5.945556 456 0.0425 2256.3 222 2177.82 6.987 7.637981 661 0.1275 2345.4 252 2472.12 5.485 5.749286 432 0.2125 2599.65 255 2501.55 5.585 5.405275 390 Load: 10 Kg from -0.0425 2648.7 261 2560.41 5.8742 6.229889 451 0.0425 2452.5 225 2207.25 7.945 8.098267 665 0.1275 2648.7 265 2599.65 5.8742 5.943732 418 0.2125 2795.85 265 2599.65 5.45 5.625472 381 12 Kg from ( Experimental) Copyright 2013 Published by IJESR. All rights reserved 349

-0.0425 2943 289 2835.09 6.027 6.537302 441 0.0425 2646 255 2501.55 8.2125 8.844842 690 0.1275 2943 296 2903.76 6.027 6.185387 403 0.2125 3041.125 296 2903.76 5.628 5.883437 370 Table 6: Comparison between theoretical results (Using CFD) and Experimental results For Modified Model Model Column1 Column2 Column3 Column4 Column5 Column6 Column7 2 Kg from ( Experimental) -0.1275 1187.01 122 1196.82 3.96 4.100114 240-0.0425 1177.2 117 1147.77 4.18 4.093944 234 0.0425 1177.2 120 1177.2 4.18 4.06044 233 0.1275 1187.01 124 1216.44 3.96 3.266541 229 4 Kg from (Theoretical al) ( Experimental) (Experimental ) (theoretical al) (Experimental ) Temperatur e -0.1275 1324.35 145 1422.45 4.15 3.97473 257-0.0425 1314.54 138 1353.78 4.48 4.663078 162 0.0425 1314.54 140 1373.4 4.48 4.598215 237 0.1275 1324.54 146 1432.26 4.15 3.727674 230 6 Kg from ( Experimental) -0.1275 1863.9 200 1962 4.35 4.407936 292-0.0425 1814.85 183 1795.23 5.025 5.104463 220 0.0425 1814.85 183 1795.23 5.025 4.862672 297 0.1275 1863.9 188 1844.28 4.35 4.090621 270 8 Kg from ( Experimental) -0.1275 2452.5 240 2354.4 5.5125 5.451164 340-0.0425 2256.3 220 2158.2 6.125 6.01562 259 0.0425 2256.3 227 2226.87 6.125 6.298965 313 0.1275 2452.5 253 2481.93 5.5125 6.048429 341 10 Kg Copyright 2013 Published by IJESR. All rights reserved 350

from ( Experimental) -0.1275 2943 295 2893.95 5.9875 6.269705 390-0.0425 2795.85 275 2697.75 6.235 6.557043 342 0.0425 2795.85 280 2746.8 6.235 6.696941 369 0.1275 2943 298 2923.38 5.9875 6.532959 383 12 Kg from ( Experimental) -0.1275 3139.2 308 3021.48 6.1245 6.233964 405-0.0425 2992.05 292 2864.52 6.69545 6.377008 380 0.0425 2992.05 290 2844.9 6.69545 6.387746 394 0.1275 3139.2 309 3031.29 6.1245 6.176116 395 7. OBSERVATION From table 5 and 6 it can be easily concluded that experimental results matches with the results of CFD analysis. Also pressure, velocity and temperature distribution in header is more uniform for modified design as compared to existing design. For making conclusions most important observations are enlisted below. Table 7: Results obtained for existing Model Load(kg) Volumetric Efficiency Mechanical Efficiency BSFC (Kg-hr/kW) 2 58.67636 80 3.294316 4 55.32073 88.75 1.695764 6 63.37818 94.167 1.18706 8 70.52073 93.125 0.996515 10 74.47273 93 0.803968 12 79.44727 90.83 0.705004 Table 8: Results obtained for modified Model Load(kg) Volumetric Efficiency Mechanical Efficiency BSFC (Kg-hr/kW) 2 69.09091 77.5 4.297587 4 78.23273 90 2.29234 6 76.94545 90 1.55096 8 88.50909 91.25 1.234824 10 88.50909 93 1.005358 12 82.98182 90 0.85303 Copyright 2013 Published by IJESR. All rights reserved 351

100 90 80 70 60 50 40 30 20 10 0 0 5 10 15 Volumetric Efficiency (Modified Model) Volumetric Efficiency (Existing Model) Volumetric Efficiency VS Load Fig 10: Comparison between Volumetric Efficiency of two Models 100 90 80 70 60 50 40 30 20 10 0 0 5 10 15 Mechanical Efficiency (Modified Model) Mechanical Efficiency(Existing Model) Fig 11: Comparison between Mechanical Efficiency of two models 8. CONCLUSION From CFD analysis it was found that manifold geometry has a significant impact on the volumetric efficiency of the engine. It was concluded that the modified design gives better volumetric efficiency. The results of CFD analysis were subsequently proved by experimental analysis. Also more uniform pressure distribution and velocity distribution obtained in modified model eases out the design procedure for the exhaust manifold. Also even though there was slight variation in mechanical efficiency and brake specific fuel consumption (b.s.f.c.) the variation was found to be very small and thus no conclusion can be drawn regarding effect of manifold geometry on mechanical efficiency and b.s.f.c. Thus we conclude that Volumetric efficiency and thus power output of the engine can be improved significantly by deployment of suggested modified design. REFERENCES [1] Muthaiah PLS, Kumar MS, Sendilvelan S. CFD Analysis of catalytic converter to reduce particulate matter and achieve limited back pressure in diesel engine. Global journal of researches in engineering A: Classification (FOR) 091304,091399, 2010; 10(5). [2] Kamble PR, Ingle SS. Copper Plate Catalytic Converter: An Emission Control Technique, SAE Number 2008-28- 0104. Copyright 2013 Published by IJESR. All rights reserved 352

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